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Old 09-13-2015, 08:35 AM   #1
cmipilot
 
1975 27' Overlander
Flower Mound , Texas
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7 blade at the vehicle to 7 pin on the trailer?

1975 27' Overlander which has been sitting for about 15 years. Tow vehicle is a 2000 Ford F250. Trying to get exterior lighting to work on the trailer. I took a trailer 7 PIN wiring diagram off the forum and created a pigtail with a 7 blade connector on one end and a 7 pin connector on the other end that transfers the functionality on each wire from the Fords' 7 blade connector (which is brand new, just installed that myself, careful to make sure that it matches current rv wiring standards) through the new pigtail. So, for example, the yellow wire at the truck 7 blade is "right turn signal". I put that in the brown wire position on the 7 PIN end so that the right turn signal functionality is in the correct place on the trailer, and so on. (I tried to upload a couple of photos but all I got was errors there too. Sheesh) And, of course, now nothing (none of the exterior lighting) works properly. Tried to be logical about this but obviously I'm missing something. Is a transition cord like this just a bad idea? I could really use some help from the brain trust cuz mine ain't gettin' the job done.
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Old 09-13-2015, 10:19 AM   #2
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Quote:
Originally Posted by cmipilot View Post
I took a trailer 7 PIN wiring diagram off the forum and created a pigtail with a 7 blade connector on one end and a 7 pin connector on the other end that transfers the functionality on each wire from the Fords' 7 blade connector (which is brand new, just installed that myself, careful to make sure that it matches current rv wiring standards) through the new pigtail.
No disrespect intended: Get one of these (or similar) wiring testers to make sure that the web reference you used was right, because trailer plug wiring standards changed from era to era and also depending on the application. Verify that your truck-side wiring is correct.
Then, use an ohm-meter to verify the ground connection on the trailer side; jumper that across using a temporary wire and then individually test each of the signal and taillight/clearance light circuits with the ground connected. If you plug everything in at once, then a bad ground will give you all kinds of contradictory-seeming behaviour.

Our Land Yacht has a 7-wire socket on its front; some previous owner had made up a patch cord to a modern 7 blade connector with MARR connectors but they'd simply matched colours. For the (short) tow home, we ended up with one taillight and clearance lights, but no left signal/brake and no electric brakes. Upon further testing at home, we determined that several wires in the plug needed to be swapped AND a PO had replaced the rusted taillight sockets with 1157 bulbs to which they'd soldered short pigtails; but then the pigtails were attached to the OEM wiring by a simple twist-and-electrical tape connection (which had subsequently corroded). Double whammy and we were only able to figure out what was wrong by doing one thing at a time.

I'll post pictures of this travesty when I get a build thread up...
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Old 09-13-2015, 11:14 AM   #3
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Maybe try a little contact cleaner on the cables and jacks.
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Old 09-13-2015, 11:58 AM   #4
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Adding complexity to any system can be problematic. Just put the blade connector on the trailer wiring harness and eliminate the pigtail. Leave the cover off the connector until you are sure everything is wired correctly (this will allow you to use a meter to check things). Just my 2 cents.
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Old 09-13-2015, 12:00 PM   #5
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I have a vague recollection that there are two wiring standards for 7 blade connectors. You might do a search online for the standards. They may have been changed since 1975.
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Old 09-13-2015, 12:03 PM   #6
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When plugged into trailer try using jumper wire from hot source to each pin on pig tail [blade end] to see what works on trailer, this will also tell if prob. with trailer lights, and if other, like turn signals, brakes, brake lites [same as turn signal]. Also there is a hot wire to trailer battery and a ground wire, if no ground. Another way to see if running lites work is to use 10 amp blade fuse at top of tv pig tail end [blade end], this would be at 11 and 1 oclock position. Presuming you have 12 volt battery in trailer to give power.
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Old 09-13-2015, 01:24 PM   #7
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Quote:
Originally Posted by cmipilot View Post
1975 27' Overlander which has been sitting for about 15 years. Tow vehicle is a 2000 Ford F250. Trying to get exterior lighting to work on the trailer. I took a trailer 7 PIN wiring diagram off the forum and created a pigtail with a 7 blade connector on one end and a 7 pin connector on the other end that transfers the functionality on each wire from the Fords' 7 blade connector (which is brand new, just installed that myself, careful to make sure that it matches current rv wiring standards) through the new pigtail. So, for example, the yellow wire at the truck 7 blade is "right turn signal". I put that in the brown wire position on the 7 PIN end so that the right turn signal functionality is in the correct place on the trailer, and so on. (I tried to upload a couple of photos but all I got was errors there too. Sheesh) And, of course, now nothing (none of the exterior lighting) works properly. Tried to be logical about this but obviously I'm missing something. Is a transition cord like this just a bad idea? I could really use some help from the brain trust cuz mine ain't gettin' the job done.
Round pin connectors are the only one's to use.

One grain of sand will stop a flat blade from working. Also, flat blade connectors usually corrode.

Round blade connector work because the terminals are round. Also they do not corrode.

Lastly, please aware that when torsion axles are not exercised every few months, the rubber rods will solidify. Additionally, torsion axles, even when used, only last about 25 years.

The following article will help you check them out.

The Dura-Torque Axle

Andy
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Old 09-19-2015, 12:51 PM   #8
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1975 27' Overlander
Flower Mound , Texas
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I appreciate the replies; not good news about the axles. I ran out of time in Michigan and had to be back in Texas before I could figure out a solution to the problem. Based on what I've been able to read and the help from all of you, my next attempt, in October, will focus on the grounding. Just too many weird things going on that can't be explained by improperly wired connectors. Again, I appreciate the help so far and if I can figure out how to post pictures to the forum, I know that will clarify what I'm not very good at explaining. Thanks all.
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Old 10-24-2015, 12:17 PM   #9
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1975 27' Overlander
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OK, back in Michigan to give it another try. Starting by replacing all marker lights with LED's. Next, cleaning all the taillight sockets and replacing all bulbs. I'll post additional info as req'd.
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Old 10-24-2015, 12:40 PM   #10
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7 blade at the vehicle to 7 pin on the trailer?

Quote:
Originally Posted by Inland RV Center, In View Post
Round pin connectors are the only one's to use.



One grain of sand will stop a flat blade from working. Also, flat blade connectors usually corrode.



Round blade connector work because the terminals are round. Also they do not corrode.







Andy

The round pin connectors are vastly superior to the typical "RV style" connectors.

I am in full agreement here.

Wiring made simple is this.

Plug the pigtail into the truck, remove the female socket from the trailer, get a test light, turn on the left turn signal, and hook the wire that makes the left turn work on the trailer.

Do the same for the right turn, then the running lights, reverse lights etc.

You will be left with the trailer hot line, ground, and trailer brakes to figure out.

Oh make sure the trailer ant the tow vehicle have a common ground in the process, if not hooked up, a jumper cable between the two will suffice.


Brevi tempore!
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Old 10-24-2015, 01:18 PM   #11
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OK, back in Michigan to give it another try. Starting by replacing all marker lights with LED's. Next, cleaning all the taillight sockets and replacing all bulbs. I'll post additional info as req'd.
You can also replace the bulbs in the tail lights and backup lights, with LED bulbs.

As you know, the LED's are brighter in the daytime than the originals are at night.

And yes, those LED bulbs cost more, but they provide you with the best update possible.

Safety first.

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Old 10-25-2015, 10:05 PM   #12
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1975 27' Overlander
Flower Mound , Texas
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Here's the bad news from todays' efforts. Looks like the critters who had camped out in this unit have been chewing on the wiring in addition to a lot of other stuff. I have power on all wires at the 7-way at the front of the trailer , some of which never makes it to the rear of the trailer. Also, I am looking at a broad range of wiring colors behind the tail lite housings. Green hooked up to black wires, a yellow wire on each of the corner running lites hooked to nothing, a bundle of wires behind the light nearest the center of the trailer in the rear that has red with yellow stripe, a brown with a yellow stripe, a solid brown, none of which are directly connected to the tail light assemblies. This just keeps getting better.

Question: Does the house battery and/or the Univolt complete any of the circuits for towing, such as running lites, corner marker lites and the like? I don't have a battery in the trailer right now and won't for the forseeable future because the battery tray has disassociated itself from the rest of the unit.
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Old 10-25-2015, 10:22 PM   #13
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7 blade at the vehicle to 7 pin on the trailer?

None of the running lights go through the univolt or house battery.

The good news is that the lights at the rear of the trailer and the trailer brakes can be made to work with a new harness run under the trailer. The top lights may be harder to get working, but with a little luck the wires to the front and back top lights might be ok.


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Old 10-25-2015, 10:35 PM   #14
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Check the wires with a test light well.

The test light will tell you what the function of each wire is and you can hook them up accordingly.

Remember, a wire does not care what color it is, just what it is hooked to.

It is typical that the wires that enter fixtures are not the same color as the harness wire they are connected.


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